(now going on 13 1/2 hours)
Do you foil or wrap before going into cooler??
How big are the butts? 13.5 hours seems like a long time. Wondering if your temperature gauges are off. You can try a couple other techniques for doneness:
1. If the meat has pulled back far enough from the bone (assuming it has a bone), if you can twist it out - it's done.
2. Fork test. stick a fork into it and twist it. If it twists easily (like budda) - it's done.
3. Tong test ( I created this one) - plunge your tongs into the butt. If it explodes - its done.